This invention relates generally to pinball machine flipper circuitry and more particularly, it relates to an improved solid-state flipper control circuit for controlling the operation of a pinball machine.
As is generally well known in the art of pinball machines utilizing pivotally mounted flippers, a relatively large amount of power is required for delivering strong pull on a solenoid core for the power stroke so as to move the flipper when the flipper switch is activated initially. However, a lesser amount of power is needed to hold or maintain the flipper when the flipper is already in the actuated position.
Heretofore, there is known in the prior art a pinball flipper circuitry which utilizes a high resistance solenoid holding coil and a second or low resistance coil connected substantially in parallel relationship across the holding coil. Such prior art pinball flipper circuitry arrangement as shown in FIG. 1 is described in U.S. Pat. No. 4,790,536 to Kurt W. Deger issued on Dec. 13, 1988, which is hereby incorporated by reference. In particular, the pinball game solenoid actuator 10 in the Deger patent is powered by a d.c. voltage source of about 50 volts connected between the positive terminal 12 and the ground terminal 14. The high resistance solenoid holding coil N.sub.h is connected across the d.c. voltage source through a normally-open flipper actuation switch 16. A normally-closed end-of-stroke switch 18 forms a series connection with the second or low resistance coil N.sub.s, the resulting series combination being connected in parallel across the holding coil N.sub.h.
In operation, wherein the flipper switch 16 is depressed upon game play activation, there will be generated currents through both of the coils N.sub.h and N.sub.s since the end-of-stroke switch 18 is normally closed. The combined magnetic flux from the coils N.sub.h and N.sub.s produces a sufficient force to move the flipper through the power stroke. At the end of the travel of the flipper, the end-of-stroke switch 18 is activated so as to open its contacts and thus remove the source of energy from the low resistance coil N.sub.s. As a result, only the high resistance N.sub.h is energized to maintain the flipper in its already actuated position. Upon deactuation of the flipper switch 16, the high resistance coil N.sub.h and the flipper are returned to their deactivated states.
However, this parallel coil solenoid arrangement has several significant disadvantages. Firstly, this prior art arrangement suffers from the drawback of requiring two separate coils wherein both the low resistance and high resistance coils are energized initially so as to move the flipper through the power stroke and wherein only the high resistance coil is energized to maintain the flipper in the actuated position. The use of two separate coils increases manufacturing and assembly costs.
Secondly, the prior art arrangement requires that the flipper switch be capable of making and breaking a relatively large current through the respective low and high resistance coils with an associated result of possible arcing and contact wear on the terminal contacts of the flipper switch. Therefore, it will be noted that the flipper switch must be of the type capable of withstanding high currents, such as a leaf spring type contact switch having terminal contacts formed of tungsten, and thus is more costly to manufacture. Thirdly, the prior art arrangement has the disadvantage of requiring the use of an end-of-stroke switch which not only must break the high current but also increases the number of mechanical components.
There have been attempts made in the prior art to eliminate the need for a dual-winding solenoid coil and relay. For example, U.S. Pat. No. 4,384,716 to Emmett J. Powers issued on May 24, 1983, disclosed an electronic control circuit for controlling the operation of pinball machine flippers which includes a single solenoid coil. The same winding is energized to place the flipper in an actuator position and to hold the flipper in the actuated position. A full wave rectified voltage is applied to the single solenoid coil when the flipper switch is actuated so as to place the flipper in the actuated position. When the flipper has been sensed to be in the actuator position by a flipper sensor switch and a comparator, only a partial phase of the rectified voltage is applied to the solenoid coil to hold the flipper in the actuated state until the flipper switch is deactivated. However, this Powers patent still suffers from the disadvantage of requiring the need of the flipper sensor switch.
Further, in U.S. Pat. No. 4,895,369 to Kurt W. Deger issued on Jan. 23, 1990, and assigned to the same assignee of the present invention there is shown a flipper control circuit for a pinball machine having a flipper, a flipper switch for activating the flipper, means for holding the flipper in an actuated position until the flipper switch is deactivated, and a solenoid coil for controlling the movement of the flipper in response to the voltage applied to the solenoid coil. A first voltage is applied to the solenoid coil when the flipper switch is activated. A second holding voltage is applied to the solenoid coil when the flipper is in the actuated position to hold the flipper in the actuated position until the flipper switch is deactivated. An end-of-stroke switch electrically disconnects the first voltage from the solenoid coil when the flipper is in the actuated position. However, this later Deger patent has the above discussed disadvantage of requiring a flipper switch that must be capable of making and breaking a high current as well as the necessity of using an end-of-stroke switch.